Plasma processing apparatus

Abstract

Disclosed is provides a plasma processing apparatus that processes a workpiece. The plasma processing apparatus includes: a processing container configured to accommodate the workpiece; a coaxial waveguide configured to transmit microwaves generated in a microwave generator; and a slow wave plate configured to adjust a wavelength of the microwaves transmitted from the coaxial waveguide and to introduce the microwaves into the processing container. A lower end portion of an inner conductor of the coaxial waveguide has a tapered shape of which a diameter increases downwardly, the slow wave plate has an annular shape in a plan view, and the inner surface of the slow wave plate encloses the lower end portion of the inner conductor and is located more outside than an inner surface of an outer conductor of the coaxial waveguide in a radial direction.

What is claimed is: 
     
       1. A plasma processing apparatus that processes a workpiece, the apparatus comprising:
 a processing container configured to accommodate the workpiece; 
 a coaxial waveguide including an inner conductor and an outer conductor where a lower end portion of the inner conductor has a tapered shape of which a diameter increases downwardly, and configured to deliver a microwave generated in a microwave generator into the processing container; 
 a slow wave plate having an annular shape in a plan view configured to enclose a lower end portion of the inner conductor of the coaxial waveguide with a gap, and adjust a wavelength of the microwave transmitted from the coaxial waveguide; 
 a slot plate having a flat-panel shape configured to contact with an entire area of the slow wave plate without a gap except for an area with the annular shape and radiate the microwave transmitted from the slow wave plate; and 
 a microwave-transmissive plate configured to contact with an entire area of the slot plate without a gap and introduce the microwave transmitted from the slot plate into the processing container; 
 wherein the slow wave plate is designed such that an inner surface of the slow wave plate is located more outside than an inner surface of the outer conductor of the coaxial waveguide in a radial direction, and 
 wherein the slow wave plate has an inner diameter determined based on a predetermined value of emissivity of the microwaves, wherein the predetermined value of emissivity is 95% or higher, wherein a change rate of the emissivity of the microwaves with respect to the change of a size of the tapered shape having a horizontal and vertical length of the lower end portion of the inner conductor is less than or equal to another predetermined value. 
 
     
     
       2. The plasma processing apparatus of  claim 1 , wherein the slow wave plate is disposed concentrically with the inner conductor. 
     
     
       3. The plasma processing apparatus of  claim 1 , wherein the inner surface of the slow wave plate extends in a substantially vertical direction. 
     
     
       4. The plasma processing apparatus of  claim 1 , wherein an inner diameter of the slow wave plate is set to be 60 mm.